1. Field of the Invention
The present invention relates to a float valve apparatus suitable for a fuel shutoff valve etc. for preventing fuel from flowing out the outside of a fuel tank when a liquid level of the fuel tank of, for example, an automobile rises.
2. Description of the Related Art
As a conventional float valve apparatus, a fuel outflow prevention valve of a vehicle characterized in that in a fuel outflow prevention valve of a vehicle including a tubular valve chamber in which an upper lid wall is had and the lower end is blocked by a filter and an exhaust hole of fuel vapor is upward opened in the center of the upper lid wall, a connection pipe integrally provided radially outward on the upper lid wall of the tubular valve chamber and in perpendicular communication with the upper end of the exhaust hole in the inner end, and a float which is vertically movably held in the tubular valve chamber and has a valve head capable of blocking the lower end of the exhaust hole in an upper surface, an inside diameter of the exhaust hole is made equal to an inside diameter of the connection pipe and also a valve seat ring with an inside diameter smaller than that of the exhaust hole is mounted in the lower end of the exhaust hole blocked by the valve head of the float is disclosed in the following JP-UM-A-5-30654. Then, a joint between the valve seat ring and the exhaust pipe end of the tubular valve chamber forming the fuel outflow prevention valve described above is performed by welding through an ultrasonic welding apparatus.
The ultrasonic welding apparatus includes, for example, an ultrasonic vibrator which is a generation source of vibration energy on the longitudinal axis, a pressure mechanism, a horn set in the pressure mechanism, and a jig for receiving a workpiece.
Therefore, when the valve seat ring is welded using the ultrasonic welding apparatus, the horn is vertically vibrated by vibration energy generated from the ultrasonic vibrator and this horn is abutted on the valve seat ring and the valve seat ring is pushed to the tubular valve chamber and thereby, frictional heat is generated between the valve seat ring and the tubular valve chamber and the mutual members melt each other and weld.
In ultrasonic welding between the valve seat ring and the exhaust hole end of the tubular valve chamber shown in the JP-UM-A-5-30654, the valve seat ring is welded to the tubular valve chamber by vertical vibration transferred from the horn, so that there was a possibility that the valve seat ring is welded at an angle with respect to the tubular valve chamber. Also, there was a possibility that the valve seat ring slips laterally and the center of a hole of the valve seat ring slips from the center of the float. Further, there was a possibility that due to heat generated at the time of ultrasonic vibration, a hole of the valve seat ring is deformed and its circularity reduces.
In such cases, performance of sealing between the valve seat ring and the float cannot be obtained sufficiently and as a result, here was a problem that leakage of liquid may occur.